Hydraulic starters are used in various applications to initiate start-up of industrial engines, such as diesel engines. As well, pre-lube pumps can be coupled to industrial engines to lubricate the engine with oil before start-up. Pre-lube pumps can prevent dry start-ups where insufficient oil is present in various parts of the engine, which can greatly damage key engine components, such as bearings.
One example of a prior art system is an industrial engine that includes a hydraulic starter and a pre-lube pump. This application often uses a single spool valve to manage hydraulic fluid flow between the hydraulic starter and the pre-lube pump. As such, this arrangement can result in high system pressure in the hydraulic starter line to be communicated to a return line of the pre-lube pump. This high return line pressure can cause failures in various components operated by the hydraulic system including the shaft seal on the pre-lube pump. Similar systems using a single valve to operate multiple devices typically fail in the same way.
Another drawback is when a high-pressure event occurs at the industrial engine, an exterior relief valve may dump oil back to a tank. This can cause the flow to decrease on the industrial engine side of the system. When the pressure drops and full hydraulic fluid flow resumes at the industrial engine, the surge of fluid in the return line can cause excessive backpressure in the return line. This event can cause a failure of various components such as the pre-lube pump shaft seal.